The term “dry” refers here not only to the removal of liquids, in particular the expulsion of solvents or the crosslinking of wet paint finishes, but also the gelling and so-called “burning-in” of powder coatings.
In all driers, transferring objects into and out of the actual drier chamber through the air locks is associated to a greater or lesser extent with energy losses since it is not possible to completely prevent the inflow of cold air into the drier chamber any more than it is possible to completely prevent the outflow of hot internal atmosphere from the drier chamber into the external atmosphere. In known driers of the type mentioned at the outset, so-called A-locks are used as the inlet and outlet lock. These A-locks are useful in that hot air is lighter than cold air and collects in the upper region of closed chambers. In the case of these A-locks, therefore, the object to be dried is introduced into the lock at a relatively low level and then raised by a lifting device to the level where the hot air is present, which only flows out to a certain extent through the inlet opening located at the lower level. At this higher level, the object to be dried is then introduced substantially horizontally into the drier chamber which is located as a whole at a higher level. The objects to be dried are then moved accordingly downwards in the outlet region to a lower level at which the outlet opening of the outlet lock is also located.
These known driers which operate with A-locks are disadvantageous in that lifting devices are required which involve increased expenditure on apparatus. A further disadvantage is that a continuous passage of the objects to be dried is not possible and is instead interrupted by the two vertical movements in the inlet and outlet lock. This reduces the throughput rate which can be achieved by the driers. Finally, the large spatial requirement in terms of the overall height, which is associated with A-locks, is also a notable disadvantage.
An object of the present invention is to provide a drier of the type mentioned at the outset which is economical and yet still enables high throughput rates.